Enhanced photocatalytic degradation of harmful dye and phenyl hydrazine chemical sensing using ZnO nanourchins Ahmad Umar a,b,⇑ , M.S. Akhtar c , A. Al-Hajry a,d , M.S. Al-Assiri a,d , G.N. Dar a , M. Saif Islam e a Promising Centre for Sensors and Electronic Devices (PCSED), Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia b Department of Chemistry, Faculty of Science and Arts, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia c New and Renewable Energy Materials Development Center (New REC), Chonbuk National University, Republic of Korea d Department of Physics, Faculty of Science and Arts, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia e Department of Electrical and Computer Engineering and Center for Nano and Micro Manufacturing, University of California, Davis, CA 95616-5270, United States highlights  Well-crystalline ZnO nanourchins were synthesized by facile hydrothermal process.  As-synthesized ZnO nanourchins utilized for photocatalyst and sensing devices.  Fast degradation rate of 98.5% within 80 min to the degradation of acridine orange dye.  High reproducible sensitivity of 42.1 lA mM 1 cm 2 towards phenyl hydrazine chemical. article info Article history: Received 26 March 2014 Received in revised form 27 September 2014 Accepted 30 September 2014 Available online 8 October 2014 Keywords: ZnO Nanourchins Working electrode Sensor Limit of detection Photocatalyst abstract Well-crystalline ZnO nanourchins were synthesized by facile hydrothermal process at low-temperature. X-rays diffraction patterns revealed that as-synthesized ZnO nanourchins exhibited good crystalline nat- ure with typical hexagonal wurtzite phase. From the morphological characterization, the synthesized nanomaterials consisted of uniform spines and systematically arranged on a periphery and resembled to urchin like morphology. As-synthesized ZnO nanourchins were extensively utilized for photocatalyst and sensing devices. As-synthesized ZnO nanourchins as photocatalysts exhibited a good degradation rate of 98.5% within 80 min towards the degradation of acridine orange (AO) dye under UV light illumi- nation. In sensing applications, the fabricated phenyl hydrazine chemical sensor based on ZnO nanour- chin electrode accomplished high reproducible sensitivity of 42.1 lA mM 1 cm 2 along with a good limit of detection 78.6 lM with correlation coefficient (R) of 0.98701. The enhanced sensing behavior and photodegradation of AO dye can be attributed to the large surface-to-volume ratio of as synthesized ZnO nanourchins, which provide large surface areas for the absorption of active oxygenated species. Ó 2014 Elsevier B.V. All rights reserved. 1. Introduction Owing to its unique, exotic and versatile chemical and physical properties, zinc oxide (ZnO) – a member of II-VI semiconductor family – has recently been recognized as a special material [1]. ZnO semiconductor with a wide band gap of 3.37 eV and high- exciton binding energy of 60 meV posses a variety of applications in UV lasers, light emitting diodes (LEDs), laser diodes (LDs), photo-detectors, p–n junction devices [2–5]. Due to its non-centro- symmetric structure, ZnO is well-known as a piezoelectric material in surface acoustic wave (SAW) devices for delay lines, filters, res- onators in wireless communication, and signal processing devices [6]. ZnO nanomaterials also posses other important properties like high electronic carrier mobility, large saturation velocity, high breakdown voltage, high biocompatibility, etc, which make its utilization in chemical, bio-, and gas sensors, electronic devices, surface acoustic waveguides, field effect transistors, hydrogen stor- age, dye-sensitized solar cells (DSSCs), etc. [7–12]. High biocom- patibility and unique optical properties of ZnO nanomaterials made them the potential catalytic materials for the detection and remediation of harmful organic chemicals. Recently, the color and water soluble organic compounds such as dyes are the main concern for the environmentalists. Usually, the residues from dye manufacturing, coloring and textile http://dx.doi.org/10.1016/j.cej.2014.09.111 1385-8947/Ó 2014 Elsevier B.V. All rights reserved. ⇑ Corresponding author at: Department of Chemistry, Faculty of Science and Arts, Najran University, P.O. Box 1988, Najran 11001, Saudi Arabia. Tel.: +966 534 574 597; fax: +966 7 5442 135. E-mail address: ahmadumar786@gmail.com (A. Umar). Chemical Engineering Journal 262 (2015) 588–596 Contents lists available at ScienceDirect Chemical Engineering Journal journal homepage: www.elsevier.com/locate/cej